Fire alarm



Nov. 19, 1929. H. T. MITCHELL FIRE ALARM Filed Dec. 19, 1925 Wkuamo .4g).

Patented Nov. 19, 1929 UNITED STATES PATENT OFFICE HENRY TRICE MITCHELL,OF KANSAS CITY, MISSOURI, ASSIGNOR 'IO THEODORE G. JOHNSON, OF KANSASCITY, MISSOURI FIRE ALARM Application filed December 19, 1925. SerialNo. 76,502.

My invention relates to fire alarms and my object is to provide asimple, reliable and inexpensive apparatus of this character which canbe installed at small cost in private dwellings, hotels, factories, etc.

A further object is to provide a novel switch for controlling thecircuits of the alarm apparatus, and in order that the invention may bereadily understood reference will now be had to the accompanyingdrawing, in which:

Fig. 1 is a side elevation of the apparatus constituting the inventionwith the parts in normal position in full lines and in dotted positionafter having transmitted an alarm.

Fig. 2 is a front elevation of the apparatus in the position it occupiesafter transmitting an alarm.

Fig. 3 is a longitudinal section of a container employed in carrying outthe invention.

Referring in detail to the different parts, 1 designates a metallic orother fire resistant holder of semitubular form connected at one end bya pivot 13 to the lowerend of a suitable support such as a bracket 2which is adapted to be secured to a ceiling or other support with screws12. The opposite end of the holder 1 is provided with a hook 14: forengagement with one end of an alloy or other fuse 3, the opposite end ofwhich is adapted to engage over a hook 16 depending from the upperportion of the bracket 2 as shown by Fig. 1.

4 designates a container consisting of glass or other suitablenonconducting material and secured in the holder 1 by metallic straps 6.The container 4 is provided with a quantity of conducting material,consisting preferably of mercury, which is free to travel from one endof said container to the other.

7 designates a pair of contacts extending through the end of thecontainer 4. nearest the pivoted end 13 of the holder 1. Said contacts 7together with the mercury 5, constitute a part of a normally closedcircuit including binding posts 9 and circuit wires 10 and 15. Thebinding posts 9 are supported by but insulated from the bracket 2 andhave the respective circuit wires 10 and 15 connected thereto as shownby Figs. 1 and 2.

The end of the container 1 nearest the fuse 3 has a pair of contacts 8extending therethrough and forming a portion of a normally open circuitincluding a pair of binding posts 9 circuit wires 11 and circuit wires17. The binding posts 9 are supported by but insulated from the bracket2.

In practice the holder 1 is suspended in an inclined position by thefuse 3 as shown by Fig. 1. This causes the mercury 5 to flow to thelower end of said container 1 and uncover the inner ends of the contacts8 and submerge the inner ends of the contacts 7, thereby opening thecircuit through the wires 11, binding posts 9 and the wires 17 andclosing the circuit through the wires 10, the binding posts 9 and thewires 15.

Should a fire occur in the vicinity of the appara-tus and cause thetemperature to rise sufficiently to destroy the fuse 3, the holder 1 andthe container 1 will immediately swing downwardly to the dotted lineposition Fig. 1, whereupon the mercury 5 will uncover the inner ends ofthe contacts 7 and submerge the inner ends of the contacts 8, therebyclosing the signal circuit through the wires 11, the binding posts 9 andthe wires 17, and open the circuit through the wires 10, the bindingposts 9 and the wires 15.

After the fire has been extinguished the apparatus may be reset byswinging the hold er 1 upwardly to its former position and supportingits raised end with a new fuse engaged over the hook 17.

From the foregoing description it is apparent that I have provided anapparatus embodying the advantages above pointed out, and while I haveshown and described one form of the invention I reserve all rights tosuch changes and modifications as properly fall within the spirit andscope of the invention as claimed.

I claim:

In a fire alarm, a thermal switch consisting of a rightangular support,a semitubular holder pivotally connected at one end to the lower end ofsaid support, a hook at the opposite end of said holder, a hook on theupper portionofthe support, afusiblelink connected to said hooks forsupporting the holder in an upwardly inclined position, a containercarried by and having its lower portion inclosed in said holder andprovided with a liquid conductor, contacts projecting into one end ofthe container which are covered by said conductor when the holder isheld in upward- 1y inclined position, and contacts projecting into theopposite end of said container which are engaged bv the conductor whenthe holder swings downwardly on destruction of the fusible link.

HENRY TRICE MITCHELL.

